A major issue in research on motor systems is the contribution made by sensory input from moving appendages to the generation of the rhythmic pattern of motor output that underlies repetitive behaviors. The purpose of the proposed research is to investigate this issue, using cockroach walking movements as a model system. Cockroaches with one or more legs missing are known to use different sequences of leg movements (and therefore different patterns of motor activity) than do those with all legs intact. These differences have been attributed to the loss of input from specific sense organs on the missing legs. This attribution will be tested and the importance of sense organs in pattern generation will be assessed by studying the effect on leg motor patterns of a variety of experimental manipulations: amputating one or more legs, focally destroying specific sense organs, and stimulating sense organs at times when they are not normally active. Standard electrophysiological techniques will be used to record neuromuscular activity and stimulate sensory nerves during walking in freely moving animals. The research is expected to yield significant new information about the way sensory information is used by an animal to generate a coordinated motor pattern, and by extension, to increase our understanding of the neural mechanisms in humans that help coordinate motor performances.